Cerebral Hernia

From the Dutch Poland Club

By Peter Jones


Breeders of fowl the world over have reported a condition that seems peculiar to crested breeds, particularly birds with heavier crests than others. The onset of the condition is described as a wobble in the head which can increase in severity to the point where the head twists right around. . In some cases the bird looses its balance and mobility altogether. This is commonly called ‘cerebral hernia’.

The Victorian Institute of Animal Science has conducted post mortems on breeds such a Polish and Silkies over the years. They confirm the existence of a mutation in the dominant gene for a crest. A mutation is a genetic copying error or mistake that occurs when the DNA from the parent bird’s meet and divide incorrectly in what is known as meiosis.

The skull of a crested fowl is unique. Unlike other breeds, it is dome-like in structure and, in heavily crested chicks, there is a tendency for the skull to be underdeveloped. Like the fontanels of a human baby, the skull of crested fowls has openings.

These are supposed to fuse in the normal way and usually do. However, this does not always occur and the result is exposure of the cerebellum (brain). Subsequently, a bird’s brain space remains venerable to the environment.

Certain lines seem more predisposed to this condition, whereas other lines are seldom affected. Unsurprisingly, it is rare in adult birds, as their skulls have had the time to grow and fuse over. It is more prevalent with young birds between 1 and 4 months of age.

Conditions and treatment.

  • Conditions
    There are a variety of causal factors and distinct conditions each of which can display the symptoms described above.
    • Type One
      Cerebral trauma or brain damage can actually happen to any young bird of any breed. It involves direct impact (ie a peck on the head) resulting in brain damage. Crested breeds could fare worse in such a situation. The brain is forced by the pressure of the impact and can ‘herniated’, swell or ooze out through the cranium.
    • Type Two
      Cerebral oedema or swelling of the cerebellum is an internal reaction to the environment and can occur in at least two ways. 

      Firstly, as a response to hot weather and change, an excess of fluid builds up as in the brain cavity, placing pressure on the centers of the brain, which govern mobility. The bird experiences vertigo (spinning sensation) and consequently loses its sense of balance. If left untreated this can lead to permanent brain damage. On occasion birds may recover and live with a permanent, but slight head wobble, continuing to eat and live with certain normality. 

      Secondly, the same symptoms can occur with a respiratory condition. The immune system can respond to the invasion of bacteria or a virus by producing more fluid with similar results.
  • Treatment
    • Prevention
      Prevention is better than cure. By ensuring that your birds are vaccinated and well managed the breeder can keep disease challenge to a minimum and avoid the third scenario. Identifying lines that have this propensity and breeding away will help avoid heartbreak. Controlling temperature in extremes of weather can prevent this condition to some degree and ensuring that no foreign objects pose a threat to the birds’ welfare (ie checking perches, feeders etc are secure are all good preventative measures).
    • Cure
      There is no guaranteed cure if you have a bird with the condition. However, a vet friend administered an intramuscularly injection of cortisone with positive results. In this case the drug reduced the inflammation/swelling and the bird recovered. 

      Other breeders have found that administering broad -based antibiotics have worked. The problem is that without a postmortem, you cant always isolates the cause. By then it is probably too late anyway. 

      At the earliest detection of the condition I would use both cortisone and Baytril (antibiotic) to cover my bases. The longer a bird is left untreated, the harder it is to achieve recovery.
Fortunately, the problem is not common. Edan Montgomery claimed that out of over 600 birds bred last year, about 5-6 developed the condition. Sadly, it is usually the heavily crested potential champs.

By hatching in large numbers, line breeding rather than close in breeding, and practicing good management techniques, this condition is largely avoidable. Every breed has its hiccups. For crested breeds, this is one of them.

On a positive note, the rewards of producing a champion far outweigh the occasional disappointment linked with this condition. It also goes to show the largely detrimental nature of mutations. They are rarely if ever an advantage!

Brown Egg Blue Egg